This invention relates to a method of welding a friction material to a retainer to produce a friction member.
In the past, friction material has been attached to a retainer by either a mechanical or brazing bond. A typical mechanical bond is disclosed in U.S. Pat. No. 2,784,105 where the sintered friction material is held in a retainer cup by crimping the sides of the cup against the friction material. Unfortunately, under certain load circumstances, it is possible to separate the friction material from the retainer cup. In an attempt to increase the bonding strength between the friction material and the retainer cup, a screen was welded to the bottom of the cup. When the friction material, in powder form, was placed on top of the screen and a compressive force applied to compact the powder into the desired shape, the powder passed through the holes in the screen and formed a matrix. The matrix locked the friction material to the retainer cup. The friction material and retainer cup were then placed in an oven to sinter the friction material. Upon removal from the oven, the sides of the cup are crimped to further strengthen the retaining bond. Unfortunately, in this process, the oven size needs to be large enough to hold both the friction material and the retaining cup.
Typical examples of brazing bonds are disclosed in U.S. Pat. Nos. 3,528,807 and 3,761,256. In such brazing bonds, a material is located between a preformed friction material and the bottom of a retainer cup. When the friction material and retainer cup are placed in a sintering oven, the brazing material alloys with the friction material and the retainer cup to provide a bond which holds the friction material and retainer together. Unfortunately, because of the cost of the brazing material and the thermal energy required to heat the oven during sintering, friction materials utilizing brazing bonds have limited customer acceptance.